A common design requirement in automotive electronic applications is the provision of circuitry to protect electronic devices from damage due to reverse voltages. Most commonly, reverse voltages occur when the source (battery) cables are mistakenly reversed, or when improperly attempting to jump-start a disabled vehicle. A more intense, but limited duration situation occurs when the source voltage is suddenly interrupted, as may occur due to a loose or severed cable or connector; in such a case, interrupted reactive loads can produce relatively high reverse voltage transients that quickly damage electronic switching devices such as power transistors.
The need exists, therefore, to provide protection from reverse voltage damage, whether due to reversed battery connections, or source voltage interruptions.